JP2008535374A - Method and apparatus for providing robust reception in a wireless communication system - Google Patents

Abstract

  A transport stream carrying a program of a particular channel has an auxiliary channel, which carries a plurality of low resolution programs associated with other channels. If the location of the receiver makes it difficult for the receiver to receive a particular channel, the receiver will tune to a strong signal associated with the other channel and reduce the desired program from the auxiliary channel transmitted there. The resolution version can be played.

Description

This application claims the benefit of US Provisional Application No. 60 / 666,077, filed March 29, 2005.

  The present invention relates generally to communication systems, and more particularly to wireless systems (eg, terrestrial broadcast, cellular, Wi-Fi (Wireless-Fidelity), satellite, etc.).

In many wireless communication systems, a major problem is that the receiver may not be able to receive transmissions on some, but not all, channels (or signals). For example, in the US terrestrial broadcast television (TV) system, a city may typically have 5-15 terrestrial transmitters that are geographically separated. Each terrestrial transmitter broadcasts content on a specific channel. However, because of the geographical location of the TV set, the TV set may only receive a subset of the channels that are broadcast in a given geographic region. In fact, ATSC-DTV (Advanced Television Systems Committee-Digital Television) system (for example, United States Advanced Television Systems Committee, "ATSC Digital Television Standard", Document A / 53, September 16,1995 and "Guide to the Use of the In a modern digital communication system such as ATSC Digital Television Standard ", Document A / 54, October 4, 1995), it is well known that the reception area of a predetermined area changes depending on the position of the TV set. This is further illustrated in FIG. The geographical area has terrestrial ATSC-DTV transmission towers T ₁ , T ₂ , T ₃ and T ₄ that broadcast content related to channels 1, 2, 3 and 4, respectively. (For purposes of this example, assume that each transmission tower broadcasts only a single channel program.) In this geographic region, two TV sets (TV set 10 and TV set 20) are located. ing. As shown by the dotted arrows in FIG. 1, the TV set 10 can only receive a subset of the available channels (ie, channels 2, 3, and 4). Similarly, the dotted arrows in FIG. 1 indicate that the TV set 20 can only receive channels 1, 2 and 4.

  Today there are no measures that can mitigate this problem.

  Currently, the ATSC-DTV system provides approximately 19 Mbit / sec (million bits / second) for transmission of MPEG2 compressed HDTV (high definition TV) signals (MPEG2 is a Moving Picture Expert Group (MPEG) -2 Systems Standard Standard). ISO / IEC 13818-1)). Thus, about 4-6 standard definition TV channels can be safely supported on a single physical transmission channel (PTC) without congestion. In addition, sufficient bandwidth remains in the transport stream to provide a plurality of additional lower bandwidth unconventional services (weather forecast, stock index, headline news, home shopping, etc.). In fact, with the improvement of MPEG2 encoding and the introduction of advanced codec (coder / decoder) technology (such as H.264 or VC1), additional reserve capacity is available on the PTC.

  It has been discovered that this spare capacity can be utilized to provide a method and apparatus for providing robust reception in a wireless communication system. In particular, in accordance with the principles of the present invention, a transport stream carrying a program on a particular channel has an auxiliary channel that carries a plurality of low resolution programs associated with other channels. Thus, if the receiver location makes it difficult for the receiver to receive a particular channel, the receiver will tune to a strong signal associated with the other channel and transmit the desired program from the auxiliary channel transmitted there. Can be played back.

  In an embodiment of the present invention, the TV provider's ATSC-DTV transmitter transmits a digital multiplex transmission having a main channel and an auxiliary channel. The primary channel has one or more high definition TV (HDTV) channels provided by the TV provider, but the auxiliary channel is a plurality of channels associated with channels broadcast by other ATSC-DTV transmitters. Rebroadcast low-resolution programs.

  According to another embodiment of the invention, an ATSC-DTV receiver performs a method for providing robust reception of terrestrial video signals. Illustratively, the ATSC-DTV receiver first tunes to the PTC associated with the desired channel. If the ATSC-DTV receiver determines that the signal is not available (eg, the associated received signal strength indicator (RSSI) is below a predetermined value), the ATSC-DTV receiver may It tunes to the PTC and, upon detection, plays the desired program from the auxiliary channel transmitted there.

  In another embodiment of the present invention, the program content is embodied in a data transmission signal having at least one carrier wave, and the data transmission signal represents a plurality of packets carrying the program content of at least one main channel and auxiliary channel. The auxiliary channel rebroadcasts low-resolution program content from other channels.

  Except for the inventive concept, the elements shown in the drawings are well known and will not be described in detail. Further, it is assumed that the user is familiar with television broadcasting and a receiver and will not be described in detail here. For example, except for the concept of the present invention, NTSC (National Television Systems Committee), PAL (Phase Alternation Lines), SECAM (Sequential Couleur Ave Memoire), and ATSC (Advanced Television Standards). Assumes that you are familiar with the recommendations. Similarly, except for the concept of the present invention, a transmission concept such as 8-VSB (eight-level vestigial sideband), QAM (Quadrature Amplitude Modulation), and a receiver configuration such as an RF (radio-frequency) front end. Elements or parts of receivers such as low noise blocks, tuners, demodulators, correlators, leak integrators, squarers are envisaged. Similarly, formats for generating transport bitstreams and encoding methods (such as the Moving Picture Expert Group (MPEG) -2 system standard (ISO / IEC 13818-1)) are well known and will not be described here. It should be noted that the concepts of the present invention may not be described here because they may be implemented using conventional programming techniques. Finally, like numbers in the drawings represent like elements.

An exemplary configuration of ATSC-DTV terrestrial broadcasting according to the principles of the present invention is shown in FIG. This drawing is similar to FIG. 1, except that one or more transmission towers shown in FIG. 2 transmit signals in accordance with the principles of the present invention (described below). In this example, transmitter 100 is associated with a transmission tower T ₂ that transmits signal 111 in accordance with the principles of the present invention. Other transmission towers T ₁ , T ₃ and T ₄ may or may not have similar transmitters in accordance with the principles of the present invention. Similarly, the receivers illustrated by TV sets 200 and 205 are also adapted to utilize transmission signals that provide robust reception in accordance with the principles of the present invention. As can be seen from the dotted arrows in FIG. 2, the TV set 200 can only receive a subset of the available channels (ie, channels 2, 3, and 4). Channel 1 reception is too bad or nonexistent. Similarly, the dotted arrows in FIG. 2 indicate that the TV set 205 can only receive channels 1, 2, and 4 for effective viewing of content. The TV set 205 is similar to the TV set 200 (described below) and will not be further described here. For purposes of this example, each transmission tower is illustratively associated with a particular TV provider, which transmits the program on a single channel. For example, transmission tower T ₁ broadcasts a program on channel 1.1, transmission tower T ₂ broadcasts a program on channel 2.1, transmission tower T ₃ broadcasts a program on channel 3.1, and transmission tower T ₄ broadcasts the program on channel 4.1. Each channel number uses an ATSC major-minor channel number format, as is known in the art. However, the present invention is not limited to this. For example, transmission tower _{T 1} may broadcast a program more than one channel (e.g. channel 1.1, 1.2, etc.). Similarly, the transmission tower may not be associated with a particular TV provider.

With reference to FIG. 3, an exemplary embodiment of a transmitter 100 is illustrated. Other than the inventive concept, the transmitter 100, as known in the art, to form the ATSC-DTV signal 111 to be transmitted via the transmission tower _{T 2} of the FIG. The transmitter 100 includes a modulator 110, a low resolution encoder 115, a memory 120, and a processor 105. The latter represents one or more microprocessors and / or digital signal processors (DSPs) and may have additional memory (not shown) for executing programs and storing data. In this regard, memory 120 represents the memory of transmitter 100 and includes some memory, for example, processor 105 and / or modulator 110 and / or low resolution encoder 115. Referring also to FIG. 4 at this point, FIG. 4 shows an exemplary flowchart according to the principles of the present invention used in the transmitter 100.

  In accordance with the principles of the present invention, in step 160, transmitter 100 forms an auxiliary channel. In particular, the transmitter 100 receives the program content of each of the other channels via the signal 114 and encodes the program data at a low resolution via the low resolution encoder 115. The latter provides auxiliary channel data 116, which represents a statistically multiplexed data stream of low resolution programs associated with other channels. In this example, the programs on channels 1, 2, 3 and 4 of FIG. 2 are provided via auxiliary channel data 116 even at low resolution. It should be noted that the low resolution encoder 115 represents one or more encoders that provide low resolution program content. Accordingly, other variations are possible. For example, the transmitter 100 may have an array of low resolution encoders, each low resolution encoder receiving program content from one provider. Further, each low resolution encoder may use a different encoding or compression format. Alternatively, the auxiliary channel may be formed somewhere and provided directly to the transmitter 100 for rebroadcast as part of the PTC or the like. In step 165, processor 105 receives data associated with each of the PTCs (PTC (0) -PTC (K−1), where K> 0) via signal 104 and stores the “master” stored in memory 120. Program guide (MPG or G) "is formed. Except for the inventive concept, the processor 105 forms MPEG as is known in the art (eg, “ATSC Standard: Program and System Information Protocol for Terrestrial Broadcast and Cable (Revision B),” Doc. A. 65B, Advance Television Systems Committee, and therefore not described here). As can be seen from FIG. 3, the MPG has the respective data or information of the PTC indicated by the MPG data related to the PTC (K-1). The data associated with each PTC has a modulation format and the like, and data associated with each of the M program channels that are part of a particular PTC. Further, according to the principles of the present invention, the MPG has auxiliary channel information 121, which has a different PID from that formed in step 160 for packets carrying low resolution data. Except for the same program data and PID data found in each of the M program channels. Note that the value of M may vary from one PTC to another. It should also be noted that the MPG may be formed in other ways (eg, data representing the MPG is received by the processor 105 from an external source so that the transmitter 100 does not need to form the MPG. May be)

Finally, in step 170, the transmitter 100 forms a transport stream having a main channel and an auxiliary channel. Particularly, the modulator 110 receives the signal 109, 114 and 106, form a transport stream (or digital multiplexing) as represented by PTC111 in FIG. 3 to be transmitted via the transmission tower _{T 2} of the FIG. 2 To do. Signal 109, as is known in the art, representative of the data streams to transmit one or more high definition TV (HDTV) channels offered by TV provider associated with transmission tower T _2. Signal 116 is the aforementioned auxiliary channel, and signal 106 represents MPG 123. The modulator 110 provides the PTC 111 with an appropriate carrier frequency, and in accordance with the principles of the present invention, the transport stream has a main channel and an auxiliary channel.

  Referring now to FIG. 5, an exemplary format of a PTC according to the principles of the present invention is illustrated. The PTC 111 represents a data transmission signal having at least one carrier wave (not shown), and the data transmission signal represents a plurality of packets carrying program content of at least one main channel and auxiliary channel. The auxiliary channel carries low-resolution program content from other channels. In particular, the PTC 111 represents a stream of packets 70. The stream of packets includes at least one MPG (G) packet 75, at least one content (C) packet 80, and at least one auxiliary packet (A) packet 90. Each content packet 80 has a packet identifier (PID) and content (video, audio and / or data). For example, the content may relate to video and / or audio of a particular program channel and may relate to data representing an executable program downloaded to the receiver 300. In accordance with the principles of the present invention, auxiliary packet 90 represents low resolution data that conveys a program at low resolution, at least some of which are associated with channels transmitted by other ATSC-DTV transmitters. To do. Illustratively, the content packet 80 carries an HDTV signal.

  Reference is now made to FIG. 6, which shows a diagram of the main and auxiliary channels for the terrestrial broadcast configuration shown in FIG. As can be seen from FIG. 6, the main channel of the PTC 111 has a program of major-minor channel number 2.1, and the auxiliary channel is major-minor channel number 1.1, 2.1, 3.1, and 4. Has one program. As described above, the concept of the present invention is not limited to this. For example, the main channel may have other programs (for example, channels 2.1 and 2.2). Furthermore, the auxiliary channel need not have the low resolution form of the main channel for its transmitter (in this example, the auxiliary channel need not have 2.1).

From the foregoing, the wireless system may provide an improved coverage area of the geographic area. Assuming there are N transmitters in the city, (N−k, k> 0) may be reliably received by more than 90% of the receivers in the area. If the provider agrees to share some reserve capacity with the PTC, this reserve capacity is allocated to the auxiliary channel. Thus, the auxiliary channel carries one or more channels and can improve coverage even at reduced resolution. For example, only the providers associated with transmission towers T ₁ and T ₂ may agree to share capacity. In this case, the auxiliary channel transmitted by T ₂ are, may have only reduced resolution of the program T _1. In the above example, 3 Mbit / sec reserve capacity is available in the PTC, and the station is 1 Mbit / sec (depending on the individual channel whether this is a constant bit rate or an average 1 Mbit / sec variable bit rate) May choose to share the three other stations (T ₁ , T ₂ and T ₃ ) with each other in the auxiliary channel. In this case, the remaining 2 Mbit / sec reserve capacity can be used to provide other services. It should be noted that the PTC reserve capacity may be generated, for example, by selecting the number of main channels and limiting the transmission of the main channel so that the required amount of reserve capacity is generated at the PTC. An extreme example is the transmission of the only main channel as shown in FIG. Alternatively, MPEG2 encoding enhancements and advanced codec (coder / decoder) technology (such as H.264 or MPEG-4 Part 10 or VC1, also known as AVC (Advanced Video Coding)) to generate spare capacity in PTC The introduction of can be used.

  A high level block diagram of an exemplary TV set 200 according to the principles of the present invention is illustrated in FIG. The TV set 200 includes a receiver 300 and a display 220. Illustratively, receiver 300 is an ATSC compatible receiver. The receiver 300 may also be NTSC (National Television Systems Committee) compatible (ie, having an NTSC mode of operation and an ATSC mode of operation so that the TV set 200 can display video content from NTSC broadcasts or ATSC broadcasts). It should be noted. For simplicity in describing the inventive concept, only the ATSC mode of operation is described here. The receiver 300 receives (for example, via an antenna (not shown)) a broadcast signal 111 that performs processing for reproducing an HDTV (high definition TV) video signal applied to, for example, a display 220 for viewing video content. .

  In accordance with the principles of the present invention, the receiver 300 can also reproduce a low resolution signal for viewing when the selected channel is received too poorly or not present. Referring to receiver 300, an exemplary portion of receiver 300 in accordance with the principles of the present invention is illustrated in FIG. The receiver 300 includes a front-end filter 305, an analog / digital (A / D) converter 310, a demodulator 390, a forward error correction (FEC) decoder 395, a transport processor 350, a controller 355, and a memory. 360. Both transport processor 350 and controller 355 each represent one or more microprocessors and / or digital signal processors (DSPs) and may have memory that executes programs and stores data. In this regard, the memory 360 represents the memory of the receiver 300 and includes, for example, some memory of the transport processor 350 and / or the controller 355. An exemplary bi-directional data and control bus 301 couples various of the elements of FIG. 8 together as shown. The control bus 310 is merely exemplary, for example, individual signals (in parallel and / or serial form) may be used to communicate data and control signaling between the elements of FIG. The front-end filter 305 down-converts and filters the received signal 111 and provides a substantially baseband signal to the A / D converter 310. A / D converter 310 samples the downconverted signal, converts the signal to the digital domain, and provides a sequence of samples 311 to demodulator 390. The latter performs demodulation of signal 311 and provides demodulated signal 391 (eg, a sequence of signal points) to FEC decoder 395. The latter examines the in-phase (I) and quadrature (Q) components of each signal point of the signal 391 demodulated at the symbol rate 1 / T and sets the signal to a possible set of transmission bits represented by the decoded signal 396. Decode to The decoded signal 396 is provided to the transport processor 350, which distributes the video, audio and data bits represented by the content signal 351 to the appropriate next circuit (not shown). It should be noted that the transport processor 350 illustratively has a high resolution decoder (H) 370 and a low resolution decoder (L) 380. In this regard, it should be noted that the receiver 300 may further process the content before applying it to the display 220 via the signal 331 and / or provide the content directly to the display 230. . Note that the presence of high and low resolution decoders in transport processor 350 is not necessary. It should also be noted that receiver 300 may receive commands (eg, program selection) via a remote control (not shown).

  To understand the advantages of the inventive concept, attention is directed to FIG. FIG. 9 shows an exemplary flowchart for providing robust reception of wireless signals at the receiver. For purposes of this example, assume that receiver 300 has already received the MPG format. With the exception of the inventive concept, the use of MPG by a receiver to tune to a channel is known in the art. For example, U.S. Pat. No. 6,366,326 issued April 2, 2002 by Ozkan et al. And / or U.S. Pat. No. 5,946,052 issued August 31, 1999 by Ozkan et al. See Therefore, MPG search and acquisition is not described here.

  In step 505, receiver 300 (eg, controller 355) receives a channel selection from a user (not shown), eg, via the remote control. In step 510, receiver 300 (eg, controller 355) uses the information from the MPG obtained (via memory 360) to tune to the PTC associated with that channel. In particular, the front end filter 305 is tuned to the PTC via the control bus 301. In step 515, receiver 300 (eg, controller 355) checks the received signal strength indicator (RSSI) via signal 356 of FIG. If the RSSI value is greater than or equal to a predetermined value (e.g. -75 dBm (decibels for 1 milliwatt)), the reception is good and in step 520 the receiver 300 (e.g. controller) according to the obtained PID information from the MPG. 355, via transport processor 350 and high resolution decoder 370) to select packets from the main channel of the PTC. Video content from the selected packet is provided to the display 220 (this step is not shown in FIG. 9). However, if the RSSI value is below a predetermined threshold, the reception is determined to be bad. In this case, receiver 300 (eg, controller 355) attempts to find an auxiliary channel for playback of the content of the selected channel in accordance with the principles of the present invention. In particular, the receiver 300 tunes to another PTC at step 525 and checks the RSSI value again at step 530. If the reception is bad, the receiver 300 continues to check the available PTC indicated by the acquired MPG. If the PTC is not finally obtained, an error message is generated (not shown in FIG. 9). However, if the PTC is detected with good reception, execution proceeds to step 535. In this step, the receiver 300 receives the PTC auxiliary channel acquired according to the PID information from the MPG acquired in step 520 for the selected channel (eg, via the controller 355, transport processor 350 and low resolution decoder 380). Select packets from. Video content from the selected packet is provided to the display 220 (this step is not shown in FIG. 9), which allows the user to view the desired program even at low resolution.

  As described above, according to the inventive concept, a robust transmission and reception method is described in a system having multiple sources and multiple destinations (receivers or sinks). Indeed, the inventive concept described above can be described as a form of spatial diversity. For example, in the exemplary embodiment described above, the ATSC-DTV system of FIG. 2 incorporates spatial diversity in accordance with the principles of the present invention.

  From the foregoing, the foregoing is merely illustrative of the invention, and thus, although not explicitly described herein, those skilled in the art will embody the principles of the invention and provide numerous alternatives that fall within the spirit and scope of the invention. It can be seen that a configuration can be devised. For example, although illustrated with respect to separate functional elements, these functional elements may be embodied in one or more integrated circuits (ICs). Similarly, although illustrated as separate elements, any or all of the elements may be implemented in a stored program control processor (eg, a digital signal processor). The stored program control processor executes associated software (eg, corresponding to one or more steps illustrated in FIGS. 4 and / or 9, etc.). Further, although illustrated as elements grouped within the TV set 200, these elements may be distributed to different units in any combination. For example, the receiver 300 of FIG. 7 may be part of a device or box, such as a set top box physically separated from a device or box incorporating a display 220 or the like. Although terrestrial broadcasting (for example, ATSC-DTV) has been described, the concept of the present invention can be applied to other types of communication systems (for example, satellite, Wi-Fi, cellular, etc.). It should be noted. Indeed, although the inventive concept is shown for a stationary receiver, the inventive concept is also applicable to a mobile receiver. Thus, it will be appreciated that numerous modifications may be made to the concepts of the invention and that other configurations may be devised without departing from the spirit and concept of the invention as defined in the claims.

Reception problems in the terrestrial television broadcasting area Terrestrial broadcasting according to the principle of the present invention An exemplary block diagram of a transmitter embodying the principles of the present invention. An exemplary flowchart according to the principles of the present invention used in the transmitter of FIG. Part of an exemplary signal format in accordance with the principles of the present invention Diagram of main and auxiliary channels for the terrestrial broadcast configuration shown in FIG. Exemplary high level block diagram of a receiver embodying the principles of the present invention. Exemplary portion of a receiver embodying the principles of the invention Exemplary flowchart for use in a receiver according to the principles of the present invention.

Claims (17)

A data transmission signal carrying a transport stream and having at least one carrier,
The transport stream has a plurality of packets carrying program content of at least one main channel and auxiliary channel;
The auxiliary channel is a data transmission signal for rebroadcasting low-resolution program content from at least one other channel.   The data transmission signal of claim 1, wherein the main channel transmits at least one high-definition TV channel.   The data transmission signal according to claim 1, wherein the main channel represents an Advanced Television System Committee-Digital Television (ATSC-DTV) signal. A transmitter having a modulator that forms a physical transmission channel (PTC) for broadcasting,
The PTC represents a digital multiplex transmission having a main channel and an auxiliary channel;
The main channel has one or more high resolution video channels;
The auxiliary channel is a transmitter that re-broadcasts one or more low-resolution video programs associated with channels broadcast by other transmitters.   The transmitter of claim 4, wherein the high-definition video channel is a high-definition TV channel.   The transmitter according to claim 4, wherein the main channel of the PTC represents an Advanced Television Systems Committee-Digital Television (ATSC-DTV) signal. A demodulator for receiving a transport stream carrying a main channel and an auxiliary channel;
And a processor for selecting content from the auxiliary channel to view the selected channel.   The receiver according to claim 7, wherein the main channel carries at least one high-definition TV channel.   The receiver according to claim 7, wherein the main channel represents an Advanced Television System Committee-Digital Television (ATSC-DTV) signal.   The processor selects the auxiliary channel to watch instead of the main channel corresponding to the selected channel for a viewing area with bad reception of the main channel or a viewing area without reception of the main channel. Item 8. The receiver according to Item 7. A method used in a transmitter,
Forming a physical transmission channel (PTC) to broadcast,
The PTC represents a digital multiplex transmission having a main channel and an auxiliary channel;
The main channel has one or more high resolution video channels;
The auxiliary channel rebroadcasts one or more low resolution video programs associated with a channel broadcast by another transmitter.   The method of claim 11, wherein the high-definition video channel is a high-definition TV channel.   The method of claim 11, wherein the main channel of the PTC represents an Advanced Television Systems Committee-Digital Television (ATSC-DTV) signal. A method used in a receiver,
Tune to a physical transmission channel (PTC) not associated with the selected channel;
Replaying the selected channel from the auxiliary channel conveyed in the PTC;
The auxiliary channel transmits a program at a low resolution. The tuning step includes:
Determining whether the receiver is in a bad reception area or non-reception area of the PTC associated with the selected channel;
15. The method of claim 14, comprising tuning to a PTC that is not associated with the selected channel if the receiver is in a poor reception area or non-reception area of a PTC associated with the selected channel.   15. The method of claim 14, wherein the main channel carries at least one high definition TV channel.   The method of claim 14, wherein the main channel represents an Advanced Television System Committee-Digital Television (ATSC-DTV) signal.

Images